Inhibition of corrosion of zinc in 0.01M H2SO4 by 5-AMINO-1- cyclopropyl-7-[(3R,5S)3,5-dimethylpiperazin-1-yl]-6,8-difluoro-4-oxoquinoline- 3-carboxylic acid (A)

Effect of A on the corrosion of zinc has been studied by using weight loss and gasometric methods. The study revealed that A inhibits the corrosion of zinc with corrosion efficiency ranging from 34.64 - 73.50%. The kinetics of uninhibited and inhibited corrosion reactions of zinc is found to be first order. Values of rate constant and half-life ranged from 0.1076 - 1.10893 and from 24 - 154days respectively. An average value of activation energy (Ea) of the inhibited corrosion reaction (5.1751J/mol) was higher than average values of activation energy obtained for the uninhibited corrosion reaction (-13.0760J/mol). Also average values of enthalpy change (ΔHads =- 15.1751J/mol) and entropy change (ΔSads = -279.8631J/mol) indicated that the adsorption of A on zinc surface is exothermic and is accompanied by increase in degree of orderliness. Between 303 and 323K, values of free energy of adsorption (ΔGads) ranged from -84.7852 - -90.3805KJ/mol indicating that the adsorption of A is spontaneous and follows the mechanism of chemical adsorption. Lagmuir adsorption isotherm has been found to be applicable to the adsorption of A on mild steel surface. © 2007 University of Manchester and the authors.